Genotype: N / N [ Homozygous normal ]
The dog is noncarrier of the mutant gene.
It is very unlikely that the dog will develop Progressive Retinal Atrophy ( PRA4 ). The dog will never pass the mutation to its offspring, and therefore it can be bred to any other dog.
Genotype: N / PRA4 [ Heterozygous ]
The dog carries one copy of the mutant gene and one
copy of the normal gene.
It is very unlikely that the dog will develop Progressive Retinal Atrophy ( PRA4 ) but since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%.
Carriers should only be bred to clear dogs.
Avoid breeding carrier to carrier because 25% of their offspring is expected to be affected (see table above)
Genotype: PRA4 / PRA4 [ Homozygous mutant ]
The dog carries two copies of the mutant gene and
therefore it will pass the mutant gene to its entire offspring.
The dog is likely to develop Progressive Retinal Atrophy ( PRA4 ) and will pass the mutant gene to its entire offspring